The present invention relates, in general, to the planning and implementing of medical procedures, and, in particular, to a new and useful method for planning, simulating and conducting a medical procedure such as a cardiac treatment procedure as well as a new and useful systematic method for treating atrial fibrillation under ultrasound guidance and a new and useful method for planning, simulating and conducting a medical procedure for preventing macro-reentrant circuits from occurring in the atrium of the heart.
As is well known in the medical field, atrial fibrillation is a major disease state and is characterized as a common sustained cardiac arrhythmia and is widely known to be a major cause of stroke. This condition is perpetuated by reentrant wavelets, such as macro-reentrant circuits, propagating in an abnormal atrial-tissue substrate with conduction heterogeneity and altered refractory period. Various approaches have been developed to interrupt these macro-reentrant circuits wavelets, including surgical or catheter-mediated atriotomy.
A common approach for treating atrial fibrillation is through the use of radio-frequency (RF) ablation energy using an ablation catheter. In using an RF ablation catheter, continuous linear lesions are formed by ablation in order to segment the heart tissue of the atrium. By segmenting the heart tissue, no electrical activity can be transmitted from one segment to another. Preferably, the segments are made very small in order to be able to sustain the fibrillatory process.
As a result, several catheter ablation techniques may be used to treat atrial fibrillation by ablating lines in the left atrium. The relevant anatomical features involved in this type of procedure are schematically illustrated in FIG. 1B. Typically, for this purpose, the physician attempts to ablate lines in the left atrium 10 around the ostia of the pulmonary veins (13, 14, 16 and 18), in order to isolate foci of the arrhythmia. The physician may also ablate lines along the mitral isthmus connecting the right inferior pulmonary vein to the mitral valve 20 and/or the left atrial appendage ridge between the left superior pulmonary vein and the left atrial appendage 22.
And, as can be greatly appreciated, ablation of structures in the left atrium can be a-very complex and even tricky procedure and is heavily dependent upon the individual skill of the operating physician. Part of the procedure complexity includes accessing the left atrium 10 in an efficient and safe manner. Thus, in order to properly reach or access the left atrium 10, the physician must pass a sheath 40 through the vena cava into the right atrium, and then through the interatrial septum 11 at fossa ovalis 12 and into the left atrium 10. The physician then must pass an ablation catheter 50 through the sheath 40 into the left atrium 10, and must then position the catheter 50 at a succession of locations that define the ablation lines. The procedure is shown schematically in FIG. 1B. Optimal deployment of the sheath 40 and catheter 50 for these purposes varies substantially from patient to patient, due to a high level of anatomical variability. Failure to position and operate the medical devices or procedure tools correctly may result, at the least, in failure to fully isolate a focus of the arrhythmia, and can cause fatal complications. As a result, left atrial ablation has a sub optimal success rate.